I'll be referring to events that have happened in book 1, A Game of Thrones, so you might want to skip this post if you don't want to read any spoilers.
So, A Clash of Kings picks up with Jon heading north of the Wall with the Night's Watch (to rout the Others and/or wildings, both of which sound like a bad idea), Arya has been rescued by Yoren and is now disguised as a boy destined for the Wall (but will be dropped off at Winterfell on the way by), Catelyn and Robb are at Riverrun where they have Jaime held prisoner, Sansa is stuck in King's Landing with Cersei and her crazy-inbred son Joffrey, Tyrion has been dispatched to King's Landing to sort out the mess Joffrey caused by beheading Eddard Stark, and Daenerys, well, she's still wandering around Essos but now she has her own tribe and three dragons.
Dragons, holla. But they are baby dragons and need protecting. (Oh, and Bran and Rickon are still at Winterfell, boring.)
GRRM's world gets a little bigger and then a little bigger. We meet ever more characters, learn complicated backstories. It's impressive and ultimately very, very readable. Once you have a favorite character (Tyrion, Jon, Sansa - who gets progressively more sympathetic because you have to remember she's only, what, eleven and currently caught in a metaphorical pit of vipers, and a new character, Davos) you have to read madly to find out just what happens to that person in the next chapter (flipping back to the table of contents to see when they might next appear). The amazing Battle of the Blackwater sequence closes the King's Landing portion (echoed in Jon's fight with the wildings). Since this is book two of a projected seven, and considering the character everyone thought would last through the end (Eddard) got the chop on the steps of Baelor's sept, it's hard to tell where GRRM is going. Which is the mark of a master storyteller, in my opinion.
*I have since listend to the audio book, still narrated by Roy Dotrice, and IT IS AMAZING. Again.